In a modern city, residents spend an average of 70% of time indoors every day. Therefore, there is a great demand for functions such as positioning in an indoor environment and navigation, people search, and object search that are derived from the positioning. When arriving at the ground, a satellite signal is relatively weak and cannot penetrate a building. Consequently, the existing GPS (Global Positioning System, Global Positioning System) cannot be directly used for positioning in an indoor environment. Basically, a wireless communication manner such as a Bluetooth beacon based, a Wi-Fi (Wireless Fidelity, Wireless Fidelity) AP (Access Point, access point) based, or a macro base station based positioning technology is used for current indoor positioning. For the Bluetooth beacon based and Wi-Fi AP based positioning technologies, a terminal side implements positioning on the terminal. For the macro base station based positioning technology, a network side server performs positioning on a terminal connected to a network.
From a perspective of an implementation means, an RSSI (Received Signal Strength Indicator, received signal strength indicator) based positioning technology is mostly used in the existing Bluetooth beacon based and Wi-Fi AP based indoor positioning technologies.
The RSSI based positioning technology is implemented according to an energy attenuation model of an electromagnetic wave that is being propagated in free space. A negative correlation relationship exists between receive strength of a signal and a propagation distance of the signal. That is, the receive strength of the signal attenuates with an increase in the propagation distance. A shorter distance between a receiver and a sender leads to higher strength of a signal received by the receiver; and a longer distance between the receiver and the sender leads to lower strength of a signal received by the receiver. The distance between the receiver and the sender may be estimated according to the receive strength of the signal received by the receiver and a known wireless signal attenuation model; and a location of the sender or the receiver may be calculated according to multiple estimated distance values.
The RSSI based positioning technology has low positioning accuracy because of two main aspects: On the one hand, the receive strength of the signal is a time-based variable. That is, when the distance between the receiver and the sender remains unchanged, the receive strength of the signal obtained by the receiver varies with time. Furthermore, large quantities of interference factors exist in an actual environment. Consequently, the simple negative correlation relationship between the receive strength of the signal and the propagation distance of the signal becomes more unreliable, and a unique location of the terminal cannot be accurately determined according to the strength of the received signal. On the other hand, large quantities of interference factors, such as a body block, traffic, and movement of a mobile object, affect the receive strength of the signal. Because of impact of these unstable interference factors, even though a user stands at a same location, the receive strength of the signal obtained by the terminal is greatly different due to factors such as a different body direction and population density. Consequently, the unique location of the terminal cannot be determined according to the strength of the received signal.
In conclusion, the RSSI based positioning technology in the prior art has relatively low positioning accuracy because of an uncertain positioning result caused by ranging and positioning based only on the strength of the received signal.